As you care for your clients from day to day you often perform the same services again and again. They are scalable and sellable, but you just don't know it because you have your nose down too close to the action. Pull back a little bit and have another look. These services you already perform can be productized. Once you turn them into a product, they can be marketed and sold as products. Your customers can sign up to pay for these productized services on a recurring model. This frees you up and stabilizes your income. And it's all built on stuff you are already doing.
Take a few minutes to listen as Einar Vollset teaches me how he does it.
For more background on his ideas and concepts, have a look at the sales page of his Productized Consulting website.